I have the lights of both my tanks on timers, now. Prior to daylight saving time, both lights came on at 7:55 A.M and went off at 6:50 P.M. Since we had to set our clocks an hour ahead on March 11, the on and off is 8:55 A.M. and 7:50 P.M. The timer doesn't know the difference, only the clocks read differently.
I use all-purpose Flourish in my tanks, and I only put it in after water changes.
My hornwort has grown extensively in the 65, and somewhat in the 20. I suspect it's getting eaten in the smaller tank.
In my 20, my java moss has gone to town, bigtime. The small clump I started with is four times its original size and a deep dark green.
I would suggest you leave your light on much, much longer than four hours. Try 12 to 14 hours. See if that makes a difference. I'll bet it does...
20 gal. high: planted; 7 white cloud minnows, several RCS, 2 blue shrimp, 5 Amano shrimp, several snails; AC50, Azoo air. 65 gal: planted; 7 rosy barbs, 3 yellow glofish,, 3 zebra danios, 1 rosy red (fathead) minnow, 5 white cloud minnows, 3 dojo loaches, 6 crimson spot rainbow fish, several snails; AC110.