I can be of some help here as I have a bit of experience with breeding plecos. Normally, in captivity they are cave spawners. It is easy to buy or even make caves for them. In the wild they find places that will work but in out tanks providing caves is the most effective option. Male claim caves but females will use sometimes use them to shelter in but do not tend to claim one. They like tight spaces for spawning.
One there are fertilized eggs the female is done and she leaves the cave. The dad then takes over. He tends the eggs which hatch out into wigglers. Dad then keeps the water circulating in the cave, and protects the wigglers. At the start there is a huge yolk sac with what looks like a pair of eyes and tiny tail which flaps attached to it. As the yolk is absorbed into the wiggler the yolk shrinks and the wiggler grows. The end point of it all is there comes a time, about 4 weeks after spawning that the yolk is all absorbed and there is a tiny free swimming pleco who has reached the time it should leave the cave and strike out on its own. If there are ovnious threats outside, the dad may try and to hold them in a bit longer.
But until they hit free swimming, they did not need to eat or be fed. But now they do. Sometime a few are reluctant to leave and dad will boot them.
Based on where the eggs were in your pics I am guessing you have no caves, So they made do with the best they could find, Small plecos have small spawns. But they can spawn regularly for extended periods once they start. For those with which I have worked, the females need about two weeks to produce new eggs. However, from spawn to free swimming is about 4 weeks. This makes the ideal spawning ratio as 2m/1fm. My preference was to work with them in groups in species tanks. But they will spawn in community type tanks. However, the fry on the glass can be very tempting food for many fish who can eat them.
It is also important that pleco fry can have foods they can handle. This means that they can rasp off or swallow easily which means tiny size compare ti what they eat when the put on size/bulk.
Clearly you have what it takes to get wigglers, (what is on the glass). At that size they will eat biofilm and anything else that is soft and small enough for them to eat.
My suggestion is to get a few caves and space them in such a way they are spread out. Ideally, place the mouth of the cave facing the front glass so you can see into the cave using a not-too-powerful flashlight. Since they are a small species, a small size pleco cave works.
Look here:
https://plecocaves.com/shop/
Any of the 1 or 1.5 inch opening caves would work. You can buy a few (3-4) of different shapes and they will figure it out. The back end must be closed. When you put them onto the tank it helps if you can do so such that the cave tilts slightly toward the back end, This minimizes the chances that a careless dad lets one or more roll out. When this happens to me I have a dedicated baster to suck them up and gently shoot them back into the cave.
edited for a ton of typos
