Hi. I have a very old inground fiberglass pool. Old as in, it was one of the first pools in my city. It's still in great shape overall but we found a crack in the stairs last summer. I "repaired" it with marine putty last year just to get is through the season. This spring we went over the stair with a fiberglass kit. It has now cracked again, near the patched area. It feels as though they need to be reinforced underneath the stairs. Is this something that can be repaired or do we have to replace the stairs? There is no liner, just fiberglass and I can't find a seam on either side of the stairs that would indicate they aren't part of the shell. The cracks aren't huge holes, but it was enough to cause us to lose almost 4 inches overnight last summer. Can I cut open that hole, fill area under stairs with gravel and then use another fiberglass kit? Lastly, can this be a diy project? I've included a picture of the stairs. The crack had just been repaired a few days before this picture and is located in the middle of the last stair. It's on the part you step on, not the riser.