they got u covered if heat problem u would see a rusty colour and the leafs would buch its a nitrogen foliar feed only when lights off because your solution will dry to the leafs and fry but that dont sound like your problem but if pressed on cash go and buy mg all purpose plant food works a hole lot better but at 1/4 strengthif your only foliar feeed your roots are not getting nutrients and send a pic its a lot easier to help