We planted 1 cantaloupe plant and it isn't doing well at all. Anyone have any tips?
It sounds like the plant might have a nitrogen deficiency. Try giving it a little bit of liquid fertilizer.
A primer on fertilizer, if you need one: Their strength is measured by 3 numbers. So you'll see something like 6-4-4 or 8-5-5 on the packaging. The first number represents nitrogen. (The second and third represent phosphorous and potassium.) Nitrogen promotes healthy, green growth. Phosphorous encourages blooming. You therefore want a fertilizer with a larger 1st number, since what you want is to green the plant up.
Follow directions on the label. Most liquid fertilizers are to be mixed with water. Too much fertilizer that's not diluted can burn the roots of the plant. Then you won't have a yellow melon, you'll have a dead one!
Noting that OP is in northern Chicago suburbs, the weather here has been way too cold for cucurbits to do well. Covering with floating nonwoven row cover held off the plants with wire hoops will raise temperatures as well as protect from cucumber beetles and squash vine borers. Uncover once the first blossoms appear as the cover keeps pollinators out as well as pests.
Because cucurbits have separate male and female blossoms and a narrow time window for pollination, having a single plant is risky in terms of fruit set. For a small planting two or three plants are usually grown together in a single hill to ensure adequate male blossoms open at the time any female blossoms are ready.