I've been trying solids off and on (mostly off) since my little guy was 6.5 mos old. He has had such a hard time with them, despite being extremely enthusiastic about eating food and having every sign of readiness.
I started with avocado and that caused foamy green stools with blood in them. A clear sign that avocado was a problem. I then held off on all solids for another month, til 7.5 months - two months ago. We have had similar upset with peaches and pears. He seems to be able to tolerate only the following - sweet potato, banana, applesauce. That is all. By 'tolerate', I mean that he still has normal stools. No mucus or blood. The issue is, even after eating any of those things, his nighttime sleep is seriously disrupted. He will wake over and over and over to nurse to the point where I get zero sleep, because he wakes to nurse before I can get back to sleep myself. We will predictably have a chunk of about three hours like this in the middle of the night, and a total of around 7-10 wakeups total. When I abstain from feeding him solids, the difference is so dramatic that it cannot be a coincidence. He wakes up only 1-3 times. I have seen this over and over.
I feel I have to choose between feeding solids and sleeping, so I only try solids maybe 1-2x/week. He is now 20 lbs and nurses like a newborn, every 2-3 hours around the clock, and I am seriously challenged to eat enough to sustain both of us. Not to mention, he throws a real tantrum whenever I am eating a meal or snack and won't give him some. Which of course happens every day. At dinner time if it isn't time for him to nurse, then my husband and I have to take turns entertaining him in the other room while we take turns eating, so he won't see the food. Otherwise he will wail all through dinner if he can't have any!!
When he was 6.5 months and having a hard time I figured it was normal, his body just wasn't ready and it could wait. But at nearly 10 months I am not so sure this is normal.