bulbs should be replaced annually, T5 are supposedly good for about 15 -18 months.
OK, the MH
at only 3 ours per day can probably go another 6 - 8 months. The T5's should go now. 420nm is True actinic and penetrates a little deeper than 460nm (more blue). You probably want to stick with 10k on the MH
. 12k will be slightly bluer, 14k more so. At 20k you can skip the T5's.
So with all bulbs in play, a 14k MH
might make the tank look too blue.