Use grounded three prong surge protectors; Extension cords, plug adaptors and halogen lamps/bulbs are prohibited.Use microwaves, crockpots, toaster ovens, coffee pots, hot plates and other cooking equipment ONLY in the kitchen and not in the bedrooms or sleeping areas.Not permit the use of the laundry machines for any person that is not a Tenant.Shall not bring bicycles into the interior of the Premises (other than the basement).Tenant shall not hold, conduct or throw any large parties in the Premises.Replace batteries in smoke and carbon monoxide detectors alarms, a smoke alarm or carbon monoxide detector without a working battery will result in a fifty-dollar ($50) penalty for each infraction.Change out any broken or defective lightbulbsAllow Landlord to use Wi-Fi (if applicable) and electric to power smart home devices (if applicable) i.e. smart locks and thermostats.

I  go in and check to see what temp the hvac is set to, fridge too, if the bought a deep freezer or additional microwaves, 100w bulbs in 60w fixtures, amount of ppl inside, fish tanks, tv's and computers, and of course the indoor 'herb' garden.

You have to invest a bit in this approach so it's not a microwave answer. 

Here are SOME examples:A unit was vacant and someone left a old microwave on the front step..

If the house had a 15 year old stove, 8 year old microwave, 8 year old refrigerator, and 12 year old washing machine I wouldn't get anything for those either no matter their condition. 

(the over range microwave doesn't work and neither does the dishwasher, so I was thinking of changing the color to stainless steel and replacing the fridge and stove as well)Any other suggestions you have would be great.

Side I'm living in: New vinyl plank floor thru out, new LED cans in living room, every room painted, added wainscoting in living room (overkill), Ecobee T-stat w/ built in Alexa (free 4 being in the industry), fully rebuilt kitchen w/ added garbage disposal, dishwasher, new refrigerator, new wall mount microwave, new stove, all new cabinets and counters etc.

There is no wrong or right here but weight your options and benefits.I personally wouldn’t reduce rent but if you were, try a little off like 25$ and maybe offer them a new microwave(cost about 300$ but you get the benefit of an upgrade appliance when they leave next year)I don’t know your market well enough to give solid advice on what you should actually do so I’m just offering perspective If they are good tenants and you want to keep them then maybe give in a little, it’s not the end of the world whatever you choose, sounds like your not in a bad spot and ideally you want to keep tenants.

Added microwave ovens as upgrade.

Paint, flooring and microwave ovens.