That's a tough one to address without a picture. My first inclination is to say, plant it, WATER it and keep watering it because I think the garden specialist might be right. Sounds like neglect...too much sun without enough water. Since Endless Summer blooms on new wood, it should rebound fairly quickly. Remove and dispose of the unsightly leaves and cut off any dead stems down to (just above)a healthy looking set of leaf buds, but first make sure they are actually dead by scraping the 'bark' with your fingernail. If there is green underneath, leave the stem alone as it is alive and may yet produce some buds. If it is dead all the way down, then cut the whole stem right down to the crown. Many hydrangeas have brownish/reddish speckles on the stems as a natural characteristic so I wouldn't worry about that. For $2.00, it's worth a try as a new one can cost up to $30.00 or so. I think it might pleasantly surprise you, but if you could post a picture, you would be able to get a much better analysis.....yg

First of all, yellowing and brown spots on the leaves of tomato plants can be a sign of different types of diseases, such as early blight, late blight, or septoria leaf spot. These diseases are usually caused by fungi that thrive in warm, humid environments and can spread rapidly in crowded, humid conditions. Based on your description, your tomato plants may be experiencing some type of fungal disease. Brown spots on the leaves, along with the white residue you mentioned, are common signs of fungal infection. Additionally, the presence of fruit flies on plants could also indicate fungal growth, as fruit flies are attracted to the sweet odor produced by fungi. To address the problem, it is important to take some steps to prevent further spread of the disease. First, you should remove all infected leaves and dispose of them in the trash, rather than composting them. This will prevent the spores from spreading to other plants. You may also consider applying a fungicide spray to the remaining leaves, especially if you see new spots appearing. As for leaf yellowing, this could be due to a variety of factors, including nutrient deficiencies, overwatering, or pests. You mentioned that your soil was low in nitrogen and phosphate, so applying organic fertilizer was a good next step. However, it can take a while for the plants to recover, as the yellowing can be the result of previous stressors. As for fruit flies, you may want to try some natural remedies, such as using sticky traps or applying a dish soap and water solution to the floor. These methods can help reduce the number of flies without the use of harmful chemicals. Finally, since you mentioned that you are a novice tomato gardener, it's always a good idea to do some research and educate yourself on common problems tomato plants can face. I would recommend visiting a website like https://thegardenplants.com/pests-diseases/leaf-problems/, which from what I've seen has quite a bit of information on leaf problems on various types of plants, although I don't think there is an article on tomatoes many of the solutions for these problems are useful regardless of the plant in question. I hope this information is useful to you and good luck with your tomato plants!

Any damage that is showing on your plants is mechanical - that means it came to be from shipping and other transport, handling or jostling. It is not the result of diseases or insects nor does it look like any watering issues. In reality, these plants look pretty darn good considering most big box stores do not take the slightest bit of care with their plants (hence the evidence of damage you are seeing). As to fertilizing, you need to identify your plants and then do a bit of research, as not all plants benefit from similar fertilization methods nor do they require it at the same time. Cacti and succulents have different needs than do tropical foliage plants and flowering houseplants (orchids, African violets, flowering gift plants) have yet another set of needs. In general, an all purpose liquid fertilizer used at 1/2 to 1/3 strength with every other watering is appropriate for most tropicals during their primary growing season (March through October) but you can get by with quite a bit less. I'd suggest you post this on the House Plants forum both to get accurate ID's on your plants and their advice as to when, how much and with what to best fertilize what you have.

2L containers are way too small for tomatoes. You should have at least 5 gallons per plant unless they're mini/super dwarf/patio tomatoes.