Can you check the meter's calibration and/or are the batteries bad?
Your EC shouldn't spike like that without some nutrient being added somehow.

When it's too hot the plants stop growing but keep transpiring, using just the water and little or no nutrients causing the nutrient concentration to increase. Water can also evaporate from your res. Causing the tds to increase. Was the water level the same or lower? Depending on your reservoir size and number/size of plants, this could be your problem if not a result of your tds meter malfunctioning.
Topping off daily with half strenght (or close) can help solve this problem.

Well the meter is brand new like 3 weeks old and i am not sure if i can calibrate it or if i remember correctly the documentation that came with it said i will never need calibration not 100% sure but the water level was the same as when i checked it the night before through the day when i checked the nutrients it varied from the original 3640 at the highest and the lowest it read and this was near the end of the day was around 2000 PPM i didn't get a chance to check it this morning so i am unsure of the PPM as of now i will check my battery and check to see if the meter can be calibrated and if so how do i go about calibrating it is there a solution i can get or is there a known PPM standard that i can use?

This thread gives a couple of recipes for making a calibration solution.
Be sure to use distilled water. The other ingredient is either calcium nitrate or table salt.
Also, In another thread, greystroke said 925mg of table salt in 1 litre will give an EC reading of 2.0. Just search this forum for "EC meter calibration" both threads were in the top 5 results.

Ok so after further investigation there is a hole for calibration but my literature says it is factory calibrated that the is suitable for most applications, DO NOT Re-Calibrate. so do I go against the advice of the manufacturer?
I also changed the batteries out this morning and the solution topped off reads about 2100 PPM

I would suggest you mix up one of those recipes I linked to before that has an expected reading and see what kind of reading your meter gives you.
After that you can see if it is accurate or you could see about having it replaced or you could just make do with what you've got. If you can get consistent results then you can still use the meter as a general gage of nutrient concentration. If a fresh batch reads 5000 on your meter then that is your baseline to decide whether to add just water of nute concentrate when you test it next time.

Well it turns out that my Nutrient solution was defiantly mixed to hot had some roots that were breaking off. kinda like root rot. so I dulled the solution down some more. still haven't figured out for the wide variety in readings but it is not doing it now it is reading steady now one time fluke Maybe not sure but mixed up one of the recipes suggested and it was 1960 PPM so is that a big deal and not sure what conversion my meter uses cause it doesn't say on the literature. but my rez has been stable since I diluted it some more a couple of days ago and plants are doing awesome now

I believe (though haven't looked back at the threads) the table salt solution had a ppm of 2000. If that is correct and the one you used, I would think 1960 was within the tolerance of your measuring devices.
Another thought occurred to me: maybe you measured your nutrients too quickly after adding them to the rez? If you didn't give them a chance to distribute over the entire volume of water and tested a "hot" spot, maybe that is why your initial reading was so much higher than later? I'm not sure this makes practical sense, but just some food for thought.

That could definitely be a possibility didn't really think about that at the time but then again after a couple of days it was still reading in that way hot in the morning and then later on in the day would be less potent but they are doing good now so i got the problem fixed now but from now on i will mix in a little then work my way up to what i want it at rather than mixing it all in at one time that way i get less waste in terms of my powdered nutrients that seems the better way to go

Well i got alot of new growth on the tomatoes so i believe i have the problem nailed down