Hmm perhaps the cinder blocks are heating your soil up a bit much. I know tomatoes will cease setting fruit if its too hot. What are you growing exactly?

Also raised beds drain and dry out faster so perhaps the plants are not getting enough water. If that's the case mulching the beds and using drip irrigation will help.

I have tomato plants as well as cucumbers, green beans, zucchini, and green peppers - carrots, spinach and lettuce are done for, but still have potatoes growing. I have been watering on a regular basis - in fact if anything, I may have been overwatering a bit. Not sure what to do about the soil heating up too much, if the cinder blocks could be causing that!

Is it possible for underground pests? Ants building a nest where you can't see?

Lots of people use concrete blocks, rocks, or brick for raised beds so there shouldn't be that much of a problem with the heat. In any case using mulch will help cool the soil and keep it from drying out as fast. I find a moisture meter very helpful in determining how dry the soil is. They are only $6 or $7. I use it so often I keep one in the front yard and the back.

We have a couple of raised beds with strawberries. By June, it's too hot for them. We stick pvc hoops over the bed & tie up some shade cloth.

The plants perk right back up. I've noticed that our local nurseries keep even full sun natives under shade cloth--of course these are container plants, but still, it must benefit them even though those plants are watered daily.

We also pick up lots of bagged oak leaves in May & mulch heavily.

I have raised beds around my front trees. The soil kept drying out so we bought some of the moisture crystals and mixed them in with the dirt. It seems to help a bit.

Looks like I'm going to try using some PVC and shade cloth to see if that helps what is left in my raised bed garden. It may be too late this season, but I need to test it out to see if there is any benefit so I can use it next spring before the heat starts taking its toll. I'm thinking it would even be a good idea when I start my fall garden in August.

Just an fyi, don't plant potatoes and tomatoes together...

I grow in raised beds made from cinder blocks too, 2 blocks high, filled with sandy loam and loads of compost. I've found that the cinder bricks can make the soil get a little alkaline, not extremely so, but a little sulfur seemed to help. My tomatoes do pretty good, my squash did amazingly so. I have some peppers and some amaranth in them this year also loving it.