Dog poop problems

My 7 year old mixed mastiff is normally regular with poop (color, form, frequency). Past 3 days his stool has been loose, mucus, yellow, more frequent,  and. More urgent.  Appetite, energy level, etc all normal. No other symptoms.  He did eat food and other stuff found on the ground (last time, last night). He did eat some bones from a soup last time was 3 or 4 days ago. Plse advise. Does he need to see a vet? What should I do at home to help make him better? Regular dog food (or chicken and rice).

Hello there - how big were these bones?  Usually, it is not a good idea to let dogs eat bones as they can have shards that spear the guts and lead to severe complications, such as peritonitis.  I am going to ignore the bones for the rest of this answer, because the risks about bones and dogs can be found a lovely article by following this link: https://vethelpdirect.com/vetblog/2022/02/12/is-it-ok-to-give-cooked-bones-to-dogs/#:~:text=In%20the%20wild%2C%20dogs%20would,should%20always%20eat%20them%20raw. If your dog has consumed a bone, it is worth asking your vet to triage the case. However, where problems happen, diarrhoea as the only symptom would be unusual.

In this case, your dog appears to have yellow, urgent diarrhoea.  I have an article about this too: https://vethelpdirect.com/vetblog/2022/02/19/why-is-my-dogs-poo-yellow/ Your vet should triage this also.  If too much fluid might be being lost, the patient may become dehydrated, so they may need to be assessed for a drip.  Another concern is that you do not sound sure what was eaten and whether it may have been toxic, but your vet can go through this with you too.  Once these more urgent matters have been dealt with, a sample may be taken.  If the cause is relatively benign and the patient remains comfortable / in good hydration, diet-related diarrhoea will frequently pass on its own, although there are things that your vet can give to help.