I wouldn't even consider more than two T5HO bulbs over each of those tanks. The 45 cm (18 inch) front to back depth means you really need two bulbs around 10 inches apart at the top of the tanks to get good uniformity of lighting over the whole substrate. And, with two bulbs widely separated you don't have the high growing plants keeping the low growers in shade all day. With 4 bulbs, as you have, you have much too high light intensity for a planted tank, so avoiding algae will be a full time job for you, one you aren't likely to succeed at.
Or, if you like having your lights suspended several inches above the tank, as I do, you can use more light. With 4 bulbs you should have the lights about a foot above the top of the tank, perhaps even higher. That is a very good way to light a tank, because it gets the light up out of the way of doing in-tank maintenance, and it gives you the most uniform light intensity in the tank.
The substrate should be about 3 -4 inches deep at the most, maybe 2 inches in the low areas. Some people use more substrate and some use less, but I think generally those are good goals to shoot for.