I didnt want to start the post with Areca Palm brown tips cause theres probably a million...however mine has brown tips.

I have an older pair of Arecas (now combined in the right pot) that I had issues with due to my lack of experience. I thought I was doing the right thing by flushing the roots but I didnt know the soil they were sold in was so so water retentive, think clay and as a resault it caused alot of root damage which killed afew fronds and damaged most of the others, ive worked hard to try and bring them back to good health and im getting new fronds growing but im sure im going to have to still cut the damaged ones back.

Anyhow that brings me to my question in around about way, ive recently purchased a new Areca in my opinion a beauty (left pot :) ) but despite lots of care and attention im getting brown crispy tips and not sure why.

Ill explain how I care for it so hopefully the problem can be identified.
Firtstly I repotted, I removed as much rubbish water retentive soil from the root ball carefully as I could then repotted with loam(john innes 2) and perlite (ive read Als write ups and am looking into pine bark mixes) im using wicks to try and remove perching water, ive potted in to slightly larger pots, I water untill water starts to drain out of the drainage holes, I water with RO only, with the new soil I only lightly fertilize with palm focus, I mist 3-4 times aday with RO water, I stand them in the porch from morning to night where it recieves lots of indirect westerly light, no full evening sun cause the window is obscured double glazed and palm is about 4ft back, temp range is from 17-30 degrees as the sun gets brighter in the day, they are on humidity trays 24/7, my hygrometer reads about average 50-60% humidity, never drops below 40% but I cant garentee its accuracy.

Ive read a few places that brown tips are normal but I dont buy that, when I bought it it had a few snipped fronds and small amount of brown tips but there are alot of fronds and most had lush and healthy tips.
Im not sure what im doing wrong, any ideas what might be causing this?

Thanks