What could this yellowing be

Hi, my plants have strarted to get yellow patches some quite big and some very small. I'll admit the temperature was 35 celcius for about 4 hours but now i've got it to 27 celcius and 21 lights off. I also noticed quite a lot of condensation building up so I took out the small pan of water I had in there today to help with humidity which I now think was doing mare harm than good. I've been feeding it just 3ml per litre of plant magic oldtimers grow (a uk organic feed which might not be heard of in the states) so I must not be overfeeding or underfeeding. These plants are 4 weeks and 3 days from seed and just now put them on 12/12. I honestly think it's condensation build up because it didn't start happening until I put the pan in there with water.The pic with the yellow patch is where it's worst but isn't as big as this anwhere on any other plants and when this first happened there was one of the new growth leaves touching the leaf where the yellow spot is now
Another thing that concerns me though is that earlier on, on the new growth on one of my plants a blade on a leaf just snapped off very easy and felt pretty dry. I am really puzzled what this is aand 'I think that it's the condensation but I don't see how the condensation would be to blame for the dry new growth or it could be heat stress and condensation working together. If anybody has any ideas what it could be please let me know guys.

hey any ideas anyone...i have the same problem...

Looks like goldmember jizzed on your plant...

light bleaching, maybe nute burn...

Problem solved you where right calikid it was light bleach. I found that my reflector wasn't opened wide enough so the reflector was only reflecting light under the light onto the plants but now i've opened the reflector all the way it is now reflecting all over my plants instead of just at one spot with extreme reflection. I already solved this issue before reading your reply but thanks anyway I would've needed that info if I didn't find the cause and solution. Plants have now recovered nicely and I noticed the new growth was turning pale green to yellow but its back to normal now.